The present invention relates to sidebooms used for pipelaying, and more particularly pertains to methods and apparatus providing a simplified control system for improving the handling of the plurality of controls for operating the boom and load of hydraulically-operated sidebooms, and for providing a plurality of apparatus for fail-safe operation of these sidebooms during pipelaying.
It is well known in the art that tractor-type vehicles having an integrated adjustable boom disposed on a side thereof are commonly used for pipelaying. Referred to as "sidebooms," such vehicles were mechanically-operated in their first incarnation and are now readily available from original equipment manufacturers in hydraulically-operated models. The use of hydraulically actuated booms and hoist assemblies is described by Stefanutti in U.S. Pat. No. 3,265,218, wherein hydraulic cylinders are used either inside or astride the boom to raise and lower the boom. The apparatus taught by Stefanutti has not been widely accepted in the art.
As taught by Vinton in U.S. Pat. No. 3,938,669, however, while the introduction of such hydraulically-operated sidebooms were anticipated to provide improvements associated with effectively and safely manipulating winches and cables through an operator's interfacing with clutches, brakes, and levers for controlling the position of the boom and for hoisting and lowering a load, such sidebooms failed to provide the prerequisite control and versatility. To attempt to remedy this deficiency in the art, Vinton discloses a hydraulic circuit that includes two separate sources of hydraulic fluid for controlling sideboom movement-related functions. One fluid source provides low volume hydraulic fluid for accomplishing not only precise, low-speed manipulation and control, but also for preventing anti-drift of both boom and hoist. The other fluid source provides high volume hydraulic fluid for providing high-speed operation of these movement and control functions. The plurality of control valves inherent in the Vinton circuit for controlling the hoist and the boom motors are operated via two levers. This apparatus also incorporates a hydraulic cylinder, instead of a drum/cable arrangement for controlling the boom; no drums or cables are involved in raising or lowering either the boom or the hook, except a short cable connected to the hook at the end of a hydraulic cylinder. As is known by those skilled in the sideboom art, this methodology was a commercial failure.
As a further development in the sideboom art, Forsyth teaches in U.S. Pat. No. 5,332,110 a hydraulically-operated sideboom intended to prevent boom over-rotation, to impart positive drive to the boom and load winches, and to provide improved control over free fall and vertical kick-out. These safe operating features are particularly intended for pipelaying applications involving lifting and lowering of large pipes.
As will be understood by practitioners in the art, the drawworks systems known in the art are operated by a sophisticated combination of clutches and brakes in order to control the cooperative movement of the boom and the load. Moreover, a drawworks system built upon a discontinued mechanically-operated, low-drive sideboom--having significantly more controls than a conventional discontinued tractor--inherently suffers from a panoply of problems associated with the simultaneous use of a daunting ensemble of gear-shifting mechanisms, clutches, and brakes, all operated by 6 different hand controls to properly lift and manipulate heavy pipes under conditions generally characterized by unpredictable and adverse terrain. Pipeline construction companies constitute approximately 95% of the users of this type of machinery. As will be appreciated by those conversant with the art, historically, such pipeline construction companies have had to choose either one of the newer high-drive sidebooms with herein before mentioned faults and high price or one of the discontinued low-drive sidebooms that are more economical but are more dangerous and are very difficult to operate. Manufacturers such as Komatsu, Fiat-Allis, Mid Western, and Caterpillar now build pipelayers with a hydraulic system that includes two to three hand controls for operating sideboom winches for handling pipes during pipelaying operations. It should also be noted that, as the pipelaying industry continues to mature, the number of skilled sideboom operators has gradually diminished.
As should be evident to those skilled in the art, it would be advantageous for construction companies who engage in pipelaying operations to have the benefit of improved handling, safety, and efficiency. It would be also advantageous for pipeline contractors to have the ability to utilize sidebooms that achieve a level of safety heretofore unmatched by any other sideboom system known in the art, regardless of design. Of course, it would be advantageous for pipelaying contractors to have the benefit of a hydraulic sideboom that inherently simplifies or mitigates the two to three controls associated with controlling the lifting and lowering of a pipe load. Accordingly, these limitations and disadvantages of the prior art are overcome with the present invention, and improved means and techniques are provided which are useful for controlling boom and load maneuvering with a single lever, for providing a fail-safe anti-tipping feature, and for providing a fail-safe anti-two-blocking feature--all of which enable efficient and safe pipelaying operations heretofore unknown in the sideboom art.